switching timeline frames in logic editor (help)
Use a mouse sensor to run an action. In the action actuator you can specify the start and end frame to play. You will need a property to track where you are and run a different part of the action for each value.

Personally I wouldn't use the action keyframes, I would use a simple motion for the camera.



When a mouse wheel up event happens and the location property is less than 4, the camera is moved 10 units on X and adds 1 to the location property. Simply repeat for the opposite direction.